1. Field of the Invention
The present invention relates to a composite switch that is used mainly in an input operation section, and the like, of a mobile communication device such as a portable telephone and a pager, and various kinds of small-sized and multifunctional electronic devices such as a remote control, an audio device, a game device, a car navigation system, and a digital camera, and operates in two stages by tilting operation of an operation section.
2. Background Art
A conventional composite switch operating in two stages by tilting operation is described in FIG. 11 to FIG. 14.
FIG. 11 is an external perspective view showing a conventional composite switch. FIG. 12 an exploded perspective view showing a conventional composite switch. FIG. 13 is a sectional view taken along line 13-13 of FIG. 11. FIG. 14 is a sectional view taken along line 14-14 of FIG. 11.
In FIGS. 11 to 14, box-like case 1, made of an insulating resin, has a square shape seen from the upper surface. In case 1, first push switch 2 to fourth push switch 5 (hereinafter, referred to as first switch 2 to fourth switch 5) are disposed in the vicinities of the four corners on the bottom surface. Furthermore, support holes 1A for swingably supporting the below-mentioned operation body 7 are respectively provided in the centers of the walls of the two opposing sides.
Fixed contact 8 includes peripheral contact 8A and central contact 8B. Fixed contact 9 includes peripheral contact 9A and central contact 9B. Fixed contact 10 includes peripheral contact 10A central contact 10B. Fixed contact 11 includes peripheral contact 11A and central contact 11B. Fixed contacts 8 to 11 are insert-molded and fixed in four recessed portions. The four recessed portions are provided two by two symmetrically with respect to a line, which is a swing center shaft of operation body 7, connecting two support holes 1A of case 1. Furthermore, the peripheral portions of the lower surfaces of circular dome-like movable contacts 2A, 3A, 4A, and 5A made of an elastic metal thin plate are brought into contact with peripheral contacts 8A, 9A, 10A and 11A, respectively. The central portions of the lower surfaces of movable contacts 2A, 3A, 4A, and 5A face central contacts 8B, 9B, 10B and 11B, respectively.
In such a configuration, contact portions of first switch 2 to fourth switch 5 are turned ON when they are pressed from the upper part of operation body 7 and turned OFF when pressing is removed.
Note here that the above-mentioned four movable contacts 2A to 5A have the same diameters and heights. However, the thickness of an elastic metal thin plate as a material is larger in movable contacts 4A and 5A at the left side (see, for example, FIG. 11) than in movable contacts 2A and 3A at the right side (see, for example, FIG. 11). Therefore, the operation force at the time of being pressed is larger in movable contacts 4A and 5A than in movable contacts 2A and 3A.
On the upper parts of movable contacts 2A to 5A of the contact portions of first switch 2 to fourth switch 5, driving bodies 2B to 5B, made of an elastic insulating material such as rubber, are mounted. When movable contacts 2A to 5A of the contact portions are pressed via driving bodies 2B to 5B, first switch 2 to fourth switch 5 operate in a large pressing operation stroke.
Furthermore, driving bodies 2B to 5B are disposed in a manner in which two each of the driving bodies symmetric with respect to the swing center shaft of case 1, that is, driving bodies 2B and 3B and driving bodies 4B and 5B are connected and integrated with each other. Thus, connected driving bodies 12 and 13 are formed of the same elastic insulating material and having the same shape and dimension. Each of driving bodies 2B to 5B can be elastically deformed independently.
Then, the upper surface of case 1 housing switches 2 to 5 is covered with metal cover 16 having four holes 16A into which the upper parts of driving bodies 2B to 5B are inserted. Above cover 16, operation body 7 made of an insulating resin is placed.
Two columnar portions 7B are inserted into two support holes 1A of case 1. Columnar portions 7B are provided on the lower parts of the opposing two sides of plate portion 7A having a square shape seen from the upper surface of operation body 7. Operation body 7 is swingably supported around a line connecting two support holes 1A as a swing center shaft. Spherical shaped top parts of four driving bodies 2B and 5B are brought into contact with the lower surface of plate portion 7A of operation body 7, respectively.
Next, an operation of a conventional composite switch configured as mentioned above is described.
In a normal state, any contact portions of first switch 2 to fourth switch 5 of the composite switch are in an OFF state.
In this state, a force for tilting operation body 7 in the front down direction is applied as shown in FIG. 11. Then, operation body 7 swings around a line, connecting two columnar portions 7B at the lower part of operation body 7 supported by two support holes 1A of case 1, as a center shaft, and tilts in the front down direction. As operation body 7 moves in the front down direction, each of the spherical-shaped top ends of driving bodies 2B and 4B, which are brought into contact with the front side lower surface of plate portion 7A, is depressed. Driving bodies 2B and 4B themselves are compressed and deformed, and at the same time, they depress movable contacts 2A and 4A of first switch 2 and third switch 4 disposed in the lower part.
However, as mentioned above, the thickness of an elastic metal thin plate forming movable contact 4A is larger than that forming movable contact 2A. Therefore, when the tilting amount of operation body 7 is larger than a predetermined value, firstly, a dome-like portion of movable contact 2A elastically bends with comfortableness. Thus, peripheral contact 8A and central contact 8B of fixed contact 8 are short-circuited via movable contact 2A.
Thus, first switch 2 is operated and its signal is transmitted to a circuit of an electronic device using this composite switch via a leading terminal (not shown) connected to each contact. At this time, as mentioned above, the operation force of movable contact 4A of third switch 4 is larger than that of movable contact 2A of first switch 2 since the thickness of material of the operation force of movable contact 4A of third switch 4 is larger than that of movable contact 2A of third switch 2. At this time, only first switch 2 having a small operation force of movable contact 2A to be bent is operated and third switch 4 is not operated.
When the force applied to operation body 7 is increased from this state, the top ends of driving bodies 2B and 4B are further depressed and driving body 2B of first switch 2 is compressed and deformed in a state in which movable contact 2A is pressed onto central contact 8B. Driving body 4B of third switch 4 is also further compressed and deformed. When the amount becomes a predetermined amount or more, and the pressing force toward movable contact 4A is beyond the operation force for bending movable contact 4A, movable contact 4A elastically bends with comfortableness. Peripheral contact 10A and central contact 10B of fixed contact 10 are short-circuited via movable contact 4A. Thus, third switch 4 is operated.
Then, when the force applied to operation body 7 is removed, in the reverse order with respect to that of the pressing operation, movable contacts 2A and 4A and driving bodies 2B and 4B restore the original shape by the restoring force. That is to say, operation body 7 is returned to the original position and first switch 2 and third switch 4 are returned to the original normal state, that is, an OFF state again.
Similarly, when a force for tilting operation body 7 in the rear down direction is applied, second switch 3 firstly operates. When the pressing force is further increased, fourth switch 5 also operates. When this pressing force is removed, fourth switch 5 and second switch 3 are turned OFF in the reverse order with respect to the above-mentioned order.
As mentioned above, by tilting operation body 7, the composite switch can operate first switch 2 and third switch 4 or second switch 3 and fourth switch 5 in two stages with different operation strokes and operation forces.
An example of prior art information related to the invention of this application includes Japanese Patent Unexamined Publication No. 2002-203460.
However, in accordance with recent diversification of various electronic devices, switches having a short tilting operation stroke or generating less operation click at the time of operation have been demanded. However, in the above-mentioned conventional composite switch, since driving bodies 2B to 5B are formed of an elastic insulating material such as rubber, there is limitation to shortening the tilting operation stroke. Furthermore, as mentioned above, when an elastic insulating material is used, sound generated when movable contacts 2A to 5A elastically bend is large, thus making it difficult to suppress the generation of noise.